The present invention relates to a disk driving apparatus for rotating a disk such as a hard disk or an optical disk.
Recently, in such a disk driving apparatus, it is necessary for a bearing which is the heart thereof to have high accuracy and reduced torque, requiring a small gas bearing with lower friction.
One example of a known gas bearing is shown in FIG. 6. In FIG. 6, reference numeral 1 denotes a chassis having a housing 2 mounted thereon. The housing 2 is provided with a shaft 4 rotatably accommodated therein and having a hub 4B. The shaft 4 has an end section 4C at the lower end and a disk flange 4A perpendicular to the shaft 4. A bottom plate 3 is attached to the housing 2 so as to be at a right angle with shaft 4. At a contact surface of the bottom plate 3 and the end section 4C, a hydrodynamic pressure generating groove 3A is formed to cause pressure between the end section 4C thereof and the groove 3A so as to rise the shaft 4 with respect to the housing 2 out of contact with bottom plate 3 during rotation because of pressure generated between the bottom plate 3 and the end section 4C. On either the outer circumferential surface of the shaft 4 or the inner circumferential surface of the housing 2, hydrodynamic pressure generating grooves 5A and 5B are formed in herringbone patterns to carry out the noncontacting rotation. A motor rotor 6 is mounted on the shaft 4 having the hub 4B at the upper end thereof and a motor stator 7 is attached inside the housing 2 confronting the rotor 6. Disks 8 and spacers 9 are alternately attached to the hub 4B and fixed by a disk fixing plate 10.
The operation of the hydrodynamic gas bearing device with the above-described construction will be described hereinbelow. Firstly, when the stator 7 is energized, the rotor 6 rises by the pressure of gas in the hydrodynamic pressure generating grooves 5A and 3A and rotates together with the shaft 4, the disks 8, the spacers 9, and the disk fixing plate 10.
However, the device with such a construction has the following problems. That is, the device has large number of parts; very high assembly accuracy between the shaft end section comprised of the hydrodynamic thrust bearing and the bottom plate 3 is required; poor assembly accuracy causes the thrust bearing to come in contact with something to prevent the shaft from rising.